Rework EventSource CORS tests to be usable from Workers.

LayoutTests/http/tests/eventsource/eventsource-cors-basic-expected.txt

-CONSOLE ERROR: EventSource cannot load http://localhost:8000/eventsource/resources/es-cors-basic.php?count=1. No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://127.0.0.1:8000' is therefore not allowed access.
-CONSOLE ERROR: EventSource cannot load http://localhost:8000/eventsource/resources/es-cors-basic.php?count=2. The 'Access-Control-Allow-Origin' header has a value 'http://some.other.origin:80' that is not equal to the supplied origin. Origin 'http://127.0.0.1:8000' is therefore not allowed access.
-Test that basic EventSource cross-origin requests fail until they are allowed by the Access-Control-Allow-Origin header. Should print a series of PASS messages followed by DONE.
+CONSOLE ERROR: EventSource cannot load http://127.0.0.1:8080/eventsource/resources/es-cors-basic.php?count=1. No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://127.0.0.1:8000' is therefore not allowed access.
+CONSOLE ERROR: EventSource cannot load http://127.0.0.1:8080/eventsource/resources/es-cors-basic.php?count=2. The 'Access-Control-Allow-Origin' header has a value 'http://some.other.origin:80' that is not equal to the supplied origin. Origin 'http://127.0.0.1:8000' is therefore not allowed access.
+Test that basic EventSource cross-origin requests fail until they are allowed by the Access-Control-Allow-Origin header.
 
-PASS: got error event and readyState is CLOSED
-PASS: got error event and readyState is CLOSED
-PASS: got cross-origin message event with data "DATA1" and lastEventId "77"
-PASS: got cross-origin message event with data "DATA2"
+On success, you will see a series of "PASS" messages, followed by "TEST COMPLETE".
+
+
+PASS es = new EventSource("http://127.0.0.1:8080/eventsource/resources/es-cors-basic.php?count=1") did not throw exception.
+PASS es.withCredentials is false
+PASS es.readyState is es.CLOSED
+PASS count != 3 && count != 4 is true
+PASS es = new EventSource("http://127.0.0.1:8080/eventsource/resources/es-cors-basic.php?count=2") did not throw exception.
+PASS es.withCredentials is false
+PASS es.readyState is es.CLOSED
+PASS count != 3 && count != 4 is true
+PASS es = new EventSource("http://127.0.0.1:8080/eventsource/resources/es-cors-basic.php?count=3") did not throw exception.
+PASS es.withCredentials is false
+PASS evt.origin.indexOf('http://127.0.0.1:8080') === 0 is true
+PASS evt.data == 'DATA1' && evt.lastEventId == '77' is true
+PASS count is 4
+PASS evt.origin.indexOf('http://127.0.0.1:8080') === 0 is true
+PASS count is 4
+PASS evt.data is "DATA2"
 DONE
+PASS successfullyParsed is true
 
+TEST COMPLETE
+